Python：从函数返回值而无需等待完成它

Question

我是python的新手，所以不确定如何实现这个但我想运行一个函数，它将返回一些虚拟值而无需等待完成它，函数必须异步完成任务。

像：

msg = {
     "status": "Process is initiated."
}

def b():
    print ("3")
    time.sleep(5)
    fh = open("hello.txt","w")
    fh.write("Hello World")
    print ("4")
    fh.close()

def a():
    print ("1")
    x = b()
    print (x)
    print ("2")

if __name__ == '__main__':
    a()


Desired Output:
    1
    {"status": Process is Initiated."}
    2

and function b should work in background and finish it work asynchronously. In this case After 5 seconds it should write into the file.